1. Field of the Invention
The present invention relates to an improvement of a blower for use in a variety of office automation equipments (hereinafter referred to as OA equipment)
2. Description of Related Art
An OA equipment such as a computer or a copying machine, etc. houses electronic circuits (a multiplicity of electronic parts) in its housing, which generates a considerable amount of heat causing a damage or a deterioration of the electronic parts because the heat is not easily released from the housing.
In particular, such OA equipment in recent years is in a downsizing trend providing a smaller size of housing while the amount of heat generated is approximately same, so that it will be more important technical task to deal with a heat-related problem. Accordingly, there has been provided a blower at a ventilation hole on a sidewall of the housing through which the heat internally generated is released out of the housing so as to prevent the electronic components from being thermally damaged.
A conventional blower of this type is hereinbelow described with reference to FIG. 3.
Reference numeral 1 in FIG. 3 denotes a casing approximately a cylindrical shape. A housing 2 is integrally formed at the center of the casing 1 and a cylindrical bearing support 3 is fitted and inserted in the center portion of the housing 2.
The bearing support 3 supports outer races of two bearings 4, 5 disposed at an interval while a shaft 6 is supported by inner races of the bearings 4, 5. A stop ring 7 is wore at a lower end of the shaft 6 which prevents the shaft 6 from being pulled out and positions the shaft 6 in the axial direction.
A reference numeral 8 denotes an impeller made of synthetic resin and consists of a cylindrical body 9 and blades 10 disposed on outer periphery of the cylindrical body 9. The impeller 8 is mounted in such a manner that the body 9 is fitted and inserted into a cup-shaped motor yoke 11.
The motor yoke 11 is connected to the top end of the shaft 6 through a zinc die-cast-made boss 12. The shaft 6 has a knurling groove 13 thereon at its connecting portion with the boss 12 to improve a tight-fitting with the boss 12. A ring-shaped permanent magnet 14 is fixed at an inner periphery of the motor yoke 11.
A stator core 16 having a stator wire 15 wound around is fixed at an outside of the bearing support 3. A circuit board mounting an electronic circuit, e.g. a PC board 17, is mounted below the stator core 16 (at a static part) so as to supply a predetermined electric current to the stator wire 15 in order to activate a unit of the stator wire 15 on the stator core 16, and a unit of the motor yoke 11 and the permanent magnet 14 to work respectively as stator and rotor for a brushless direct current motor.
The electronic circuit mounted on the PC board 17 controls an electric current supplying to the stator wire 15 in order to rotate the unit of the motor yoke 11 and the permanent magnet 14 relative to the unit of the stator wire 15 and the stator core 16. The stator wire 15 is connected to the electronic circuit on the PC board 17 through a conductive wire, not shown. Moreover, a lead wire 18 is connected to the PC board 17 so that power is supplied to the PC board 17 therethrough.
The blower thus constructed is used by mounting at a ventilation hole of a housing (not shown) of an OA equipment. The blower is normally mounted at the ventilation hole in such a manner that the upper side in the drawing faces the exterior of the housing while directing the shaft 6 to be horizontal.
When a direct current of a predetermined voltage is supplied to the lead wire 18, a current controlled by the electronic circuit on the PC board 17 flows to the stator wire 15. Then a magnetic flux is generated from the stator core 16, which rotates the motor yoke 11 and the impeller 8 at the center of the shaft 6 by mutually reacting with the magnetic flux generated from the permanent magnet 14.
As a result, air within the housing at the lower side of the drawing is sucked and releases toward the upper direction of the drawing through a air cavity 19, namely toward the outside of the housing. The interior of the housing is cooled by this ventilating performance.
As typically shown in FIG. 3, a conventional blower provides the PC board 17 disposed below the stator wire 15 and the stator core 16 without any consideration thereto such that the PC board 17 is nakedly exposed to the atmosphere. Thus, the PC board 17 is vulnerable to adverse effects of the stator wire 15 closely facing to the board and to the installation environment of the housing on which the blower is mounted.
Accordingly, over a long time use of the blower, the stator wire 15 may come into contact with the PC board 17 causing a short circuit, or a heat directly released from the stator wire 15 may deteriorate the characteristics of the electronic circuit (component 20) or insulation properties of the PC board 17.
If the blower is used in a dusty and/or a moisty environment, dust and moisture may directly settle onto the PC board 17 leading to the deterioration of the electronic circuit (components 20) or short circuit. The electronic circuit (components 20) on the PC board 17 is especially vulnerable to the dust and moisture causing an extensive reduction of insulation properties of the components. Any solution or improvement has been long waited in light of such drawback.
Furthermore, although cooling the interior of the housing, the blower itself generates heat. However, the conventional blower does not take into account the radiation effect of such self-generated heat, and therefore the heat gradually accumulates in the electronic circuit (components 20) of the PC board, which deteriorates the function thereof.
The present invention has been made in light of such drawbacks described above, and an object thereof is to provide a blower being able to prevent deterioration of the electronic control circuit (components) due to a close disposition of a stator wire.
It is another object of the present invention to provide a blower in which the deterioration of the electronic control circuit, particularly a reduction of an insulation property, due to a close disposition to the stator wire or to an installation environment is properly prevented.
It is still another object of the present invention to provide a blower, in which an increase of temperature generated by the blower itself due to an accumulated heat are prevented as much as possible in order to maintain the electronic circuit function.
To achieve the above described objects, a blower according to a first aspect of the present invention comprises a bearing disposed at the center of an approximately cylindrical casing, a shaft supported by the bearing, a motor yoke mounted on the shaft while having an impeller on an outer periphery and a permanent magnet on an inner periphery thereof, a stator core having a stator wire wound around disposed at the inner side of the permanent magnet, and a circuit board mounting an electronic circuit for supplying a predetermined amount of electric current to the stator wire which closely disposed to the stator wire and the stator core, wherein a partition plate is interposed between the stator core having the stator wire and the circuit board.
A blower according to a second aspect of the present invention comprises a similar feature of the first aspect, wherein a case portion is formed close to the stator wire and the stator core, and a circuit board is stored within the case portion.
A blower according to a third aspect of the present invention, in the second aspect comprises a motor base integrally formed with the casing, a lid member integrally formed with a bearing support member connected to the motor base in such a manner as to cover the motor base, and at least the lid member being formed of excellent thermal conductive material.
A blower according to a fourth aspect of the present invention, in the aspect 2 or 3 comprises a feature, wherein a case portion is provided with cooling fins disposed at the outer peripheral wall thereof.
An invention according to a first aspect of the present invention provides a blower which prevents a stator wire from contacting with a circuit board by a partition plate even if the stator wire is partially unwound to the circuit board over a long time usage. And, a heat generated from the stator wire is insulated with the partition plate so as to prevent the heat from directly radiating to the circuit board.
An invention according to a second aspect of the present invention provides the blower which houses the circuit board within a case portion so as to not only take the advantageous effects of the first aspect but also prevent deterioration due to an installation environment. That is, the circuit board is well protected even in a dusty and/or a moisty environment with the case portion, thereby prohibiting the dust and moisture from directly settling onto the circuit board (components) while keeping the circuit board free from deterioration or short circuit.
An invention according to a third aspect of the present invention in the aspect 2 provides the blower, wherein part of the case portion is integrally formed with a bearing support supporting a shaft. And, at least such integrally formed portion is made of a material of excellent thermal conductivity so that an increase of temperature of the blower due to a self-generating heat is minimized.
An invention according to a third aspect of the present invention in the aspect 2 or 3 provides the blower, wherein cooling fins are provided at the outer peripheral wall of the case portion so as to attain an improved effect of a heat release.